Fuel burner and process for gas manufacture

ABSTRACT

A partial oxidation burner and process for the manufacture of synthesis gas, reducing gas and other gas mixtures substantially comprising H2 and CO. A hydrocarbon, oxygen-rich gas and, optionally, H2O or some other temperature moderator are introduced into the reaction zone of a synthesis gas generator in which, by partial oxidation at an autogenous temperature in the range of about 1700* to 3500*F. and a pressure in the range of about 1 to 250 atmospheres, said synthesis, fuel, or reducing gas is produced. For example, a hydrocarbon is introduced into the reaction zone by way of the inner assembly of a novel multitube burner, and a mixture of oxygen-rich gas and steam is passed through a coaxial conduit disposed about the outside of said inner assembly. Said inner asembly comprises a central conduit of circular cross-section, having a plurality of parallel open-ended tubes extending downstream from the exit end of said central conduit and in communication therewith. The tubes terminate in a surrounding nozzle, which is the exit end of the coazial outer conduit.

United States Patent 11 1 Marion et al.

[ Sept. 11, 1973 FUEL BURNER AND PROCESS FOR GAS MANUFACTURE [75]inventors: Charles P tMarion, Mamoroneclt,

N.Y.; Blake Reynolds, Riverside, Conn.

[73] Assignee; Texaco Development Corporation,

, New York, NY.

[22] Filed; Oct. 4, 1971" 21 A No.: 186,207

[52] -U.S. Cl 239/132.3, 239/425 [51] Int. Cl B05b 15/00 [58] Field ofSearch 239/1323, 422-425 [56] I I References Cited 1 UNITED STATESPATENTS 1,721,381 7/1929 I Ellis 239/425 2,613,737 10/1952 Schwietert239/425 6/1966 Hoffert et al. 239/1323 Primary Examiner- Lloyd L. KingAttorney-Thomas H. Whaley et al.

[57] ABSTRACT A partial oxidation burner and process for the manufactureof synthesis gas, reducing gas and other gas mixtures substantiallycomprising 11 and CO. A hydrocarbon, oxygen-rich gas and, optionally, HO or some other temperature moderator are introduced into the reactionzone of a synthesis gas generator in which, by

partial oxidation at an autogenous temperature in the range of about1700 to 3500F. and a pressure in'the. range of about 1 to 250atmospheres, said synthesis, fuel, or reducing gas is produced. Forexample, a hydrocarbon is introduced into the reaction zone by way ofthe inner assembly of a novel multitube burner, and a mixture ofoxygen-rich gas and steam is passed through a coaxial conduit disposedabout the outside of said inner assembly. Said inner asembly comprises acentral conduit of circular cross-section, having a plurality ofparallel open-ended tubes extending downstream from the exit end of saidcentral conduit and in communication therewith. Thetubes terminate in asurrounding nozzle, which is the exit end of the coazial ii I Z4" s N Mv FUEL BURNER AND PROCESS FOR cAs MANUFACTURE BACKGROUND OF THEINVENTION into the reaction zone of a synthesis gas generator by way ofa simple annulus-type burner isknown in the artQI-lowever, thecombustion efficiency of such prior art burners, especially thoseoperating at low pressure, leaves much to be desired. Also, the reducingratio, i.e., the mole ratio H CO/CO H O of the gas produced iscomparatively low. By attempting to scale-up the size of prior artburners, it was found that the composition of the productvgas changedand that the amount of' unreacted particulate carbon is increased.Further, it was often necessary and costly to maintain a highoxygento-hydrocarbon ratio in the feed to the generator in order toreduce the yield of unreacted particulate carbon to acceptable levels.This higher reacted particulate carbon to acceptable levels. Thishigheroxygenlhydrocarbon ratio produced excessively high temperatures inthe reaction zone which shortened the life of I the refractory lining.

SUMMARY OF THE INVENTION More efficient partial oxidation of hydrocarbonfuels with oxygen and, optionally, with H O or some other temperaturemoderator is attainable by providing a burner comprising an innerassembly consisting of a central conduit of circular cross sectionhaving a plurality of smaller open ended tubes extending downstream fromthe exit end of said central conduit and in communication therewith. Theindividual tubes are parallel to the burner axis and to each other. Theyterminate within a surrounding nozzle, which is the exit end of acoaxial outer conduit. The coaxial conduit is disposed about saidcentral conduit providing an annular passage tehrebetween for the freepassage of one feed stream. Thus, the other feed stream passing throughtheflcentral conduit is split into a plurality of parallel streams withthe first feed material flowing between and around these streams. Normalfeed modes include oxygen, oil, or oil-stream mixtures in the tubes, andoil-stream mixture, oxygen-steam mixture, or oxygen, respectively in theannular passage. These reactant streams may also be reversed and passed,respectively, through interchanged passages. Further, in a doubleannulusmultitube embodiment, oil may be passed through the central tubes,oxygen or oxygen-steam mixtures'may be passed through an inner annulus,and steam may be passed through an outerannulus. By this mode', the lifeof the burner may be substantially increased.

DESCRIPTION OF THE INYENTION The present invention involves a novelburner and the process for the manufacture of gas mixtures rich inhydrogen and carbon-monoxide, such as synthesis gas, fuel gas, andreducinggas, by the partial oxidation of a hydrocarbon with anoxygen-rich gas such as air, oxygen-enriched air or substantially pureoxygen and, optionally, with steam or another temperature modulator. Theproduct gas mixture is produced in the reaction zone of a noncatalytic,refractory-lined, free-flow partial oxidation generator, such asdescribed in coassigned U. S. Pat. No. 2,809,104 issued to Dale M.Strasser et al.

In accordance with one embodiment of the present invention, thereactantsare introduced into the reaction zone of the gas generator by means ov anovel multitube burner. By means of said burner, a first stream ofreactants flowing parallel to the burner axis is'separated into aplurality of "smaller streams also flowing parallel to the burner axisin a bundle of spaced parallel tubes. At least one additional stream ofreactants is then interjected into the interstices between said bundleof tubes. Thus, a mixture of reactants is thereby produced which isdischarged from the burner as a well distributed blendof reactantstreams.

In further detail, a first reactant stream is passed through the innerassembly of said multitube burner. The burner inner assembly is ,made upof the central conduit having an open upstream end and a closeddownstream end, A plurality of parallel open ended tubes extenddownstream from said closed end in a direction parallel to the axis ofthe central conduit. The individual tubes are in a spaced andsymmetrical arrangement so that they do not touch each otherLFurther,each tube in the bundle is sealed into the closed end of the centralconduit and is in communication therewith. A free passage is therebyproduced forsaid first reactant stream through the central conduit andthe bundle of tubes.

A second reactant stream is passed through a concentric coaxialopen-ended conduit which is disposed lengthwise about the outside ofsaid inner assembly. A tip section at the downstream end of said.coaxial second conduit is provided for introducing said second reactantstream into the interstices between the parallel open-ended tubes andthence out through a nozzle at the end of this second conduit.Optionally, a concentric coaxial open-ended third conduit with aconverging tip may be disposed lengthwise about said concentric coaxialopen-ended second conduit. The tip section of said coaxial third conduitis provided for introducing a third fluid stream around said first andsecond fluid streams at or near the face of the burner.

In order to illustrate the invention in greater detail, reference ismade to several embodiments involving burner constructions as shown infigures of the drawing, wherein FIG. 1 is a general illustration of aburner assembly;

FIG. 2 is a diagrammatic longitudinal cross-section through thedownstream end of the burner, taken at line AA of FIG. 1 and showing anembodiment of the burner;

FIG. 3 is an end view of the burner tip shown in FIG. 2, taken atlineB-B. m

FIG. 4 is a view of another example of duit 10 in FIG. 2; and m FIG. 5is a view similar to FIG. 2, but of another embodiment of the burner inwhich two coaxial concentric conduits are disposed longitudinally aboutthe inner asscmbly.

Referring to the figures in the drawing, in FIG. 1 the burner assemblyis indicated generally as 1. Facecoaxial concooling chamber 2 at theoutermost tip of the burner is hollowed out for circulating coolingwater, entering by way of inlet pipe 3 and leaving by way of coils 4 andoutlet pipe 5. The axis of the burner is usually aligned along thecentral axis of the synthesis gas generator by means of mounting flange6. Reactant streams pass into the burner by way of inlets 7 and 8.

In FIG. 2, the downstream end of burner 1 is shown in. cross-section.This view is taken between A-A of FIG. 1 and comprises inner assembly 9and concentric coaxial conduit 10 disposed longitudinally about theinner assembly, thereby providing a free annular passage in betweenelements 9 and 10. A reactant stream enters burner l by way of inlet 7of FIG. 1 and passes directly through inner assembly 9. A second streamenters burner 1 by way of inlet 8 of FIG. 1 and passes directly intoconcentric coaxial conduit 10.

Inner assembly 9 comprises central conduit 11 of circular cross-sectionand a bundle of comparatively small diameter open-ended tubes 12. Thebundle of tubes extends downstream from the exit end of the centralconduit 11. The tubes are parallel to the burner axis and to each other.The plurality of tubes are in a spaced and symmetrical arrangement aboutthe burner axis and do not touch each other. While these tubespreferably extend close to the burner face 13 as shown in the drawing,in other embodiments of the burner, suchas shown in FIG. 5, they may beforeshortened. Central conduit 11 is open at the inlet end 14 and closedat exit end 15. Tubes 12 are sealed into the exit end of conduit 11 andare in communication therewith. Thus, a reactant stream may be freelypassed through inner assembly 9 by being passed first throughcentralconduit 11 and then through a plurality of tubes in the bundle12. The upstream portion 16 of concentric coaxial conduit 10 is open andforms an annular passage 17 with the central conduit 11 through which areactant stream may be freely passed. The downstream end 18 of coaxialconduit l is'disposed about the bundle of tubes 12. A converging nozzle19 is at the tip of the downstream end of coaxial conduit to facilitateintermixing the streams and to force a flat velocity profile across theinterstitial stream. Suitable angles of convergence at the tip are inthe range of to 90. Optionally, cooling means may be provided to coolthe burner tip, for example, face-cooling chamber 2 and cooling coils 4.

FIG. 3 is an end view of burner l in'FIG. 2 taken along 8-8. A suitablelayout of seven parallel tubes in the bundle of tubes 12 is depicted,with tube 20 passing through the axis of the burner. Shadedcross-sectional area I.A. shows the interstices between the outside sur-I in FIG.S l to 3 are shown in Table 1.

TABLE I Stream Passing; Through Stream Passing Through Inner Assemb y 9Concentric Conduit to liquid hydrocarbon fuel-Hp gaseous hydrocarbonfuel oxygen rich gas oxygen rich gas I. oxygen rich gas 2. oxygen richgas 3. liquid hydrocarbon fuel-Hp 4. gaseous hydrocarbon fuel oxygenrich gas-H O 6. liquid hydrocarbon fuel-H O The term hydrocarbon, asused herein to describe various feed-stocks, in intended to includegaseous and liquid hydrocarbon fuels. Also included by definition are(l) pumpable slurries of solid carbonaceous fuels, such as coal,particulate carbon, and petroleum coke in a carrier or moderator such aswater, or in a liquid hydrocarbon fuel, and mixtures thereof and (2)gas-solid suspensions, such as finely ground solid carbonaceous fuelsdispersed in either the moderator or a gaseous hydrocarbon.

The term liquid hydrocarbon fuel as used herein to describe liquidfeedstock is intended to include various materials such as-liquidifiedpetroleum gas; petroleum distilates and residues, gasoline, naphtha,kerosine, crude petroleum, asphalt, gas oil, residual oil, tar sand oil;aromatic hydrocarbons, such as benzene, toluene, xylene fractions, coaltar, cycle gas oil from fluid catalytic cracking operation; furfuralextract of coker gas oil; and mixtures thereof. Gaseous hydrocarbonfuels as used herein to describe gaseous feedstocks, include methane,ethane, propane, butane, pentane, natural gas, water gas, coke oven gas,refining gas, acetylene tailgas, ethylene off-gas and mixtures thereof.Both gaseous and liquid feeds may be mixed and used'simultaneously andmay include paraffinic, olefinic and aromatic compounds in anyproportion. The hydrocarbon feed may be at room temperature or may bepreheated to a temperature up to as high as about 600 to 1,200F., butbelow its crackingtemperature. The liquid hydrocarbon feed may beintroduced into the burner in liquid phase or in a vaporized mixturewith or without steam or other moderator.

v The term oxygen-rich gas, as used herein, is intended to include air,oxygen-enriched air, i.e., greater than 21 mole percent oxygen, andsubstantially pure oxygen, i.e., greater than 95 mole percent oxygen;Oxygen-rich gas may beintroduced into the burner at a temperature in therange of about ambient to 1,800F. The ratio of free oxygen to carbon inthe feedstock (O/C, atom/atom) is in the range of 0.7 to 1.5.

H 0 may be charged to the reaction zone in liquid or gaseous phase. Itmay be in the form of steam or atomized liquid water. Further, all ofthe H 0 may be mixed either with the hydrocarbon feedstock or with theoxygen-rich gas. Alternately, a portion of the steam may be intermixedwith the oxygen stream in conduit 10 in an amount less than about 25weight percent of the oxygen and any remainder mixed with thehydrocarbon. The H O may be at a temperature in the range of ambient1,000 E, or above. For example, the weight ratio of water to liquidhydrocarbon feed is in the range of about 0.05 to 6, and usually in therange of about 0.15 to 0.6 parts by weight of water per part by weightof hydrocarbon feed, according to the final use of the product gas.

60 H,O serves to moderate the temperature in the reaction zone of thesynthesis gas generator. It may also react with the other feedstreams inthe generator. Other suitable temperature moderators which may be usedin place of or in combination with H 0 include a cooled portion of theproduct gas, cooled off-gas from an integrated ore-reduction zone, e.g.,blast furnace, carbon dioxide, various off gases from other processes,an inert gas, e.g., nitrogen, and mixtures thereof.

The use of a temperature moderator to moderate the temperature in thereaction zone is optional and depends in general on the carbon tohydrogen ratio of the feed stock. For example, a temperature moderatoris generally not used with gaseous hydrocarbon fuels; however, generallyit is used with liquid hydrocarbon fuels. As'previously mentioned, thetemperature moderator' may be introduced as a component of either orboth reactant streams. In addition, the temperature moderator may beintroduced by itself via a separate outer conduit as will be describedin connection with the embodiment shown in FIG. 5.

The feedstreams are reacted by partial oxidation without a catalyst inthe reaction zone of a free-flow synthesis gas generator. Thetemperature is autogenously maintained within a range of about l,700 to3,500F. The pressure is in the range of about 1 to 250 atmospheresThemixture of product gases may have the following composition (volumepercent dry basis) assuming the inert gases are negligible: CO 33-52, H

62-42, CO 1.58, Cl-l 0.02-2, H 8 nil 2.0 and COS nil to 0.1. Unreactedparticulate carbon (basis carbon in the feed by weight) is about 0.2 to10 weight percent from liquid feeds but is usually negligible fromgaseous hydrocarbon feeds.

As previously described, by means of the subject burner a large volumeof a first reactant stream flowing through the central circular conduitis split into a plurality of separate streams of reactant fluid flowingthrough a bundle of parallel tubes. This permits the introduction of asecond stream of reactants into the the interstices surrounding thetubes. The greater the number of tubes, the better the distribution ofone reactant within the other reactant. The mixing of the reactantstreams which takes place downstream of the ends of the tubes isfacilitated by this improved distribution. Such efficient mixing'of thefeedstreams facilitates a more uniform partial oxidation of thehydrocarbon to produce H and CO. The combustion efficiency of theprocess is thus increased.

By means of the subject invention, reactions are made to proceed inlocal regions where there is less op portunity for overheating thehydrocarbon with an insufficient supply of oxygen to result in theformation of soot. Thus, the amount of unconverted particulate carbonproduced for a given oxygen to carbon atomic ratio in the feed may besubstantially reduced. Further, overburning" of the hydrocarbon toproduce carbon dioxide is substantially reduced. It is recommended thatthe subject burner be made from heat and oxidation-resistant metalalloys. j t

In the case'of liquid hydrocarbon as one of the feed streams, to improvethe atomization of the effluent stream from the burner, adifferentialstream velocity is maintained. Thus, the reactant streampassing through exit nozzle 19 in FIG. .2 is accelerated to a suitablehigh velocity and a flat velocity profile across the interstitialcross-section is provided. Atomization of the liquid stream takes placeat or near the face of the burner, producing a fine mist of hydrocarbondispersed in the oxygen and the temperature moderator. For example, aliquid hydrocarbon may be passed through each tube in the bundle oftubes 12 at a velocity of about 5 to 50 feet per second at the face ofthe burner, while a mixture of oxygen-rich gas and steam may be passedthrough annulus l7 and then accelerated in the surrounding nozzle 19 toa velocity of about 200 feet per second to sonic velocity at the face ofthe burner. In another example, an oxygen-rich gas, such assubstantially pure oxygen is passed through each tube of the bundle oftubes 12 at a velocity of about 300 feet per second to sonic velocitywhile an atomized mixture of liquid hydrocarbon and steam is passedthrough annulus 17 so as to be accelerated by the surrounding nozzle toa velocity of about 15 0 feet per second to cient to keep the partialoxidation reaction downstream from the downstream end of the burner,thereby preventing flash-back of the flame with resultant damage to theburner tip.

The individual tubes in the bundle of tubes 12, shown in FIG. 2 shouldbe long enough to permit the reactant stream flowing in annulus 17 toflow evenly into the interstices between the tubes, as shown in FIG. 3.For example, the following relationship shown in formula (1) issuggested as a minimum:

I.A./l. w. n. ,5(1 Where:

l= length of each tube t w separation between adjactent tubes atnarrowest gap,'as shown in FIG. 3

r number of tubes LA. cross-sectional area of interstices -see FIG. 3Actually, the length of the tubes in the tube bundle may range fromabout A to .12 inches or longer and preferably from about 2 to 5 inches,with greater lengths required as the number of tubes and the total sizeof the burner increases.

The number of tubes in the tube bundle and their typical sizes, i.e.,inside diameter (LDL) are shown in Table TABLE II lntemal Number ofTubes ID. of Individual Stream in Tube Bundle Tube-Inches Liquid 2 toabout 200 or more 1/16 to V4 Gaseous 2 to about 200 or more 0.090 to IPreferably, in order to obtain equal flow distribution in all of thetubes 12, the inside diameters of the tubes should be equal and theirlengths should be equal. The inside diameter of the tubes should besmall compared to the diameter of central conduit 11 in order to forcean appreciable pressure drop from the central conduit to discharge.Preferably, the ratio of length to inside diameter of the tubes shouldbeat least five. is

Preferably, the downstream exit ends of the plurality of tubes 12 andthe exit end of coaxial concentric conduit l0 terminate in the sameplane perpendicular to the burner axis at the downstream end of theburner, which may be also referred to as the burner face. In anotherembodiment of the invention the plurality of tubes terminate in a planeperpendicular to the axis of said coaxial concentric conduit, and saidplane is retracted upstream from the downstream end of the tip sectionof said coaxial concentric conduit in order to permit a limited degreeof premixing but no burning, thereby preventing damage to theends of thetubes and to the end of the tip section. In still another embodiment ofthe invention the exit ends of all of said plurality of tubes terminatein a plane perpendicular to the axis of said coaxial concentric conduit,and said plane is located downstream from the downstream end of the tipsection of said coaxial concentric conduit; for example slightlydownstream from the burner face.

Alignment pins, fins, locking lugs and other means may be used tosymmetrically space the tubes and conduits with respect to each other.

Although developed for the partial-oxidation reaction, this burner maybe used advantageously for other types of combustion of a hydrocarbon byan oxidant stream e.g., heat release in a boiler, or for producingreducing gas within a blast furnace or other ore reduction unit.

FIG. 4 is another version of a coaxial concentric conduit 21 which maybe used in place of conduit as shown in FIG. 2. Note that tip 22 ofconduit 21 is provided with a smooth ellipsoidal converging nozzle whosewalls develop into a straight cylindrical portion which is coaxial withthe burner axis near the outermost tip of. the nozzle. For example, theAmerican Society of Mechanical Engineers (A.S.M.E.) standard long-radiusnozzle is suitable. A further description of said nozzle may be foundinThermodynamics Fluid Flow and Heat Transmission by Huber O. Croft, page155, First Edition, 1938 McGraw-I-Iill Book Company.

FIG. 5 is another embodiment of the burner and provides two coaxialconcentric conduits i.e., intermediate conduit 23 and outermost conduit24, disposed about inner assembly 25. Inner annulus passage 26 and outerannulus passage 27 are thereby provided for the free passage of separatefeed streams; The purpose of the outer annulus is to provide arelatively non-reactive stream (moderator) separating thesurrounding-product synthesis gas from the feed stream in theinterstitial area. This separation is particularly desirable when theinterstitial fluid'is the oxidant, which can react rapidly withsynthesis gas close to the burner tip and cause burner tipdeterioration. In other words, the third passage is useful primarily toprovide greater burner durability rather than to promote highercombustion efficiency. The use of this protective sheath is notjustified except in those cases which would otherwise result inunacceptably short burner life.

The construction of the several elements of FIG. 5 has been previouslydescribed in connection with FIGS. 1-4. Cooling the burner is optional.For example, if desired, face cooling plate and cooling coil 4 may beadded to the burner shown in FIG. 5. Further, note that the tubes in thetube bundle do not necessarily extend to the burner face. Optionally,the ends of the tubes may be flush with or extend beyond the burnerface, i.e. the downstream end of the burner.

Typical combination of streams which may be introduced into the reactionzone of the synthesis gas generator by way of the double-annulusmultitube burner depicted in FIG. 5 are shown in Table III.

TABLE III Inner Assembly 25 Inner Annulus 26 l. hydrocarbon feed oxygenrich gal-Hp 2. hydrocarbon Outer Annulus 27 temp. moderating gasfeed-H;O oxygen rich gas temp. moderating gas temp. moderating gas Thevelocity and thickness of the sheath of temperature moderating gasleaving the burner by way of the converging nozzle on the downstream endof outer annulus 27 is preferably such as to prevent the oxygen in theinner annulus 26 from contacting and reacting with recirculatingsynthesis gas that is close enough to the burner face to cause damage tothe outer tip. For example, the exit velocity of the stream oftemperature moderating gas in outer annulus 27 may be about one halfthat of the oxygen stream.

Thus, in all cases an annular jet of steam or other moderator in outerannulus 27 serves to protect the outer nozzle from damage resulting fromcombustion between oxygen and synthesis gas at the burner tip. In somemodes, sufficient steam may be added to the other streams to facilitateatomization of the hydrocarbon feed or to prevent tip damage.

The burner size or scale is important in relating the required atomicratio of oxygen in the oxygen-rich gas to carbon in the hydrocarbon feedneeded to reach a given yield of unconverted particulate carbon in theproduct gas. The burner scale factor is (l) proportional to theinterfacial perimeter available for mixing the reactant in the tubeswith the reactant stream in the interstices'between the tubes; (2)inversely proportional to the cross-sectional of the stream (in thetubes) to be mixed; (3) inversely proportional to the relative distanceinto the interstitial stream which must be traversed by elements(molecules or turbulent eddies) of the stream in the tubes duringmixing; and (4) is a function of the Y ratio which is by definition theratio of the interstitial area (IA. of FIG. 3) to the total crosssectional area of tubes v12 based on the inside diameter of the tubes.For example, the burner scale factor as shown in formula (2) below hasbeen derived as a measure of therelative size of a burner as shown ifFIG. 2, when an oil containing stream is passed through the tubes of aburner having a Y ratio of 21.7.

P/SL 48.2 n/D gas for a given O/C, i.e., ratio of atoms of carbon in thefeed decreases, and the reducing ratio in the product gas increases.Thus, one would preferably design for the highest practical burner scalefactor to achieve minimum soot yield for a given 0/C ratio. For example,with respect to the burner shown in FIG. 2, with a Y ratio of 21.7, theburner scale factor P/SL should not be less than a minimum value of 266in order to yield 2 wt. percent particulate carbon at about l.04 O/Cratio.

EXAMPLES OF THE PREFERRED EMBODIMENT The following examples are offeredas proof of the efficacy of the present invention, but the invention isnot to be construed as limited thereto.

EXAMPLE I Reducing gas was produced in a producing gas generator by thepartial oxidation of heavy fuel oil having an API of 13 and a grossheating value of 18,300 BTU per pound by reaction with substantiallypure oxygen in the presence of steam. A 6 foot gas generator was usedconsisting of a refractory lined steel pressure vessel free fromcatalyst or any obstruction to the free-flow of materials therethrough.The combustion chamber volume was about 60 cubic feet.

The feedstreams were introduced into the reaction zone by way of amultitube burner mounted in an axial flanged port at the top of the gasgenerator. Thus, a stream of fuel oil at a temperature of about 390F waspassed through the central conduit and the bundle of seven tubes-of themultitube burner, shown in FIGS. 13 of the drawing. The burner tubesextended freely about 0.62 inches beyond the end of the central conduit.They were three-sixteenths inch outside diameter (OD) and had a 0.049inch wall. With a Y ratio of 21.7 the burner scale factor P/SL was 226.The velocity of the oil in the tubes was about 33 feet per second.

A mixture of substantially pure oxygen and steam at a temperature ofabout 360F was passed through the annulus of the burnerso that avelocity of about 850 feet per second was reached at the burner face.Pressure in the reaction zone was 30-31 psig and the weight ratio ofsteam to fuel oil was about 0.23.

When the atomic ratio of oxygen to carbon in the feed was 1.04, thereducing ratio was about 6.9. At this O/C ratio, the weight percent ofunconverted carbon in the product gas (basis weight of carbon in thefeed) was about 2.0 wt. percent. Also, the. composition of the productgas in volume percent dry basis was C 52.42, H, 43.91, C0 3.17, H 80.14, A 0.11 and N, 0.25.

In comparison, under substantially the same generator operatingconditions a one-tube conventional burner, such as shown in FIG. 2 ofthe U. S. Pat. No. 2,928,460 issued to Du Bois Eastman et al., having aburner scale factor of 33 and a Y ratio of 14.3 yielded 3.6 weightpercent unconverted particulate carbon for the same atomic ratio OIC of1.04. Further, the reducing ratio decreased to 6.4.

EXAMPLE II This example illustrates the effect of further increasing thenumber of tubes in the tip of the inner assembly, shown on FIGS. 2 and 3of the drawing.

Twelve symmetrically spaced metal tubes 0.152 inches 0D. with 0.032inches wall were used to replace the seven tubes extending from thecentral conduit in the burner described in Example 1. With a Y ratio of19.7, the burner scale factor P/SL was 291. With all other conditionsremaining substantially the same, it was found that less oxygen wasrequired with the 12 tube burner than with the 7 tube burner to producereducing gas having 2 weight percent of unconverted carbon. The O/Catomic ratio was about 1.025 for the burner with 12 tubes and 1.04 forthe burner with seven tubes, versus 1.09 for the originalburner having asingle central nozzle. Thus, by increasing the number of tubes in theburner, oxygen consumption in the gas generator is reduced at a decidedeconomic advantage. Further, reduced oxygen consumption contributes tolower temperatures in the reaction zone, which benefits the refractorylining. In other words, with a fixedO/C atomic ratio, i.e. 1.04, and allother operating conditions substantially the same, when a 7 tube burneris replaced by a 12 tube burner, the weight percent of unconvertedcarbon is reduced from 2 weight percent to about 1.4 weight percent.This result represents a 30 percent drop in the production ofunconverted carbon, and also simplifies or eliminates any purificationproblems relating to the recovery of particulate carbon from the productgas. Further, the reducing ratio 6.4 with the l-tube burner is increasedto 6.9, with the 7 tube burner and to 7.2 with the 12 tube burner. Thus,the quality of the reducing gas may be improved by increasing the numberof tubes. This per- -rnits the reduction in the volume of reducing gasnecessary for a given operation thereby reducing costs. For example, byusing mutitube burners, there is a reduction in the amount of reducinggas required to replace the metallurgical coke in an iron-ore blastfurnace for the production of molten iron. This permits equipment andpiping to be sized smaller in addition to cost savings for the reducinggas.

Although modifications and variations of the invention as set-forthabove may be made without departing from the spirit and scope thereof,only such limitations should be imposed as are indicated in the appendedclaims.

We claim:

l. A burner comprising,

an inner assembly, comprising a central conduit with a downstream endand an upstream end,said upstream end being open for admitting a firstreactant stream and said downstream end being sealed around a pluralityof tubes in symmetrical spaced relationship without touching each other,said tubes being parallel to each other and to the burner axis andextending downstream from the exit end of said central conduit and incommunication therewith, and said tubes having downstream ends fordischarging said first reactant stream; and

an open-ended coaxial concentric conduit disposed around the outside ofsaid inner assembly and in I spaced relationship therewith for providinga passageway for a second reactant stream, said concentric outer conduithaving a tip section which terminates in a converging exit nozzle forintroducing said second reactantstream into the interstices between theplurality of parallel tubes extending from said central conduit'and thento discharge.

2. The burner as described in claim 1 wherein said exit nozzleaccelerates the reactant stream flowing therein to a suitable highvelocity and provides a flat velocity profile across the interstitialcross section.

'3. The burner as described in claim 1 wherein said converging exitnozzle consists of a frusto-conical section whose minimum diameter isdownstream and nor- 4. The burner as described in claim 1, wherein thetip section of said concentric outer conduit terminates in an AmericanSociety of Mechanical Engineers, standard long-radius nozzle.

5. The. burner as described in claim 1, wherein the exit ends of theplurality of tubes and the exit end of said concentric outer nozzleterminate in the same plane perpendicular to the burner axis at thedownstream end of the burner.

6 The burner as described in claim 1, wherein the exit ends of all ofsaid plurality of tubes terminate in a plane perpendicular to the axisof said coaxial concentric conduit, and said plane is retracted upstreamfrom the downstream end of the tip section of said coaxial concentricconduit in order to permit a limited degree of premixing but no burning,thereby preventing damage to the ends of the tubes-and to the end of thetip section.

7. The burner as described in claim 1, wherein the exit ends of all ofsaid plurality of tubes terminate in a plane perpendicular to the axisof said coaxial concen tric conduit, and said plane is locateddownstream from the downstream end of the tip section of said coaxialconcentric conduit.

8. The burner as described in claim 1, wherein the inside diameters ofall of said plurality of tubes are equal, and the lengths of all of saidtubes are equal.

9. The burner as described in claim 1, wherein the quantity of saidtubes extending from said central conduit is a number selected from thegroup consisting of 2 to 200 or more.

10. The burner as described in claim 1, wherein the number of tubesextending from said central conduit is selected so as to maintain aburner scale factor P/SL 48.2 n/D of at least 266 when an oilcontaining-stream is flowing through said center conduit and an oxygencontaining stream is passing through said outer concentric conduit andthe Y ratio of the burner is 21.7 wherein:

P sum of the perimeters for all of said extending tubes (based on insidetube diameter) S =total cross-sectional area of all of said extendingtubes (based on inside tube diameter) n number of said extending tubes Dinside diameter of the downstream end of the tip section of theconcentric outer conduit.

Wherein D, inside diameter of each tube 12. And the Y ratio is the areaof the downstream end of the tip section of the concentric outer conduitless the total cross sectional area of all of the tubes extending fromthe exit end of the central conduit based on the outside diameter ofsaid tubes divided by the total area of all of said tubes based on theinside diameter of the tubes.

11. The burner of claim 1 further provided with a second open-endedcoaxial concentric conduit which is disposed about the first concentricconduit and in spaced relationship therewith, and a converging nozzleterminating said second coaxial concentric nozzle so as to provide apassageway for introducing a temperature moderating stream around theother two streams.

12. The burner as described in claim 1, wherein a stream of oxygen-richgas selected from the group con- 13. The burner as described in claim12, wherein a temperature moderator selected from the group consistingof steam, carbon dioxide, atomized liquid water, cooled portion ofproduct gas, cooled off-gas from an ore-reduction zone, and an inert gassuch as nitrogen, and mixtures thereof is admixed with the oxygen-richgas, the hydrocarbon or both.

14. The burner as described in claim 1, wherein a stream of hydrocarbonis passed through said inner assembly and a stream of oxygen-rich gasselected from the group consisting of air, oxygen-rich air containingmore than 21 mole percent 0 and substantially pure oxygen is passedthrough said concentric outer conduit.

15. The burner as described in claim 14, wherein a temperature moderatorselected from the group consisting of steam, carbon dioxide, atomizedliquid water, cooled portion of product gas, cooled off-gas from anore-reduction zone, and an inert gas such as nitrogen, and mixturesthereof is admixed with the oxygen-rich gas, the hydrocarbon, or both.

16. The burner as described in claim 1 provided with a cooling means forcooling the tip section of said coaxial concentric conduit by heatexchange with a cooling fluid.

17. The burner as described in claim 1 provided with a cooling means forcooling the tip section of said coaxial concentric conduit by heatexchange with a cooling fluid, wherein said cooling means comprises ahollowed out face-cooling plate at the downstream end of the burner andcooling coils encircling said tip section through which circulatingcooling water is passed.

18. A partial-combustion burner'for use in introducing reactants into agas generator, comprising a central passageway forintroducing a firstreactant stream into said gas generator, said central passagewaycomprising a central conduit'having a plurality of tubes extendingdownstream and in communication therewith, said tubes being parallel toeach other and to the burner axis and in symmetrically spacedrelationship without touching each other; and an open-ended coaxialconcentric outer conduit disposed about said central passageway and inspaced relationship therewith for providing a passageway for a secondreactant stream, said concentric conduit having a tip section forintroducing said second reactant stream into the interstices between theplurality of parallel tubes extending from said central conduit and fromthere into said gas generator, a converging exit nozzle terminating saidtip section so as to accelerate the second reactant stream to a suitablehigh velocity and to provide a flat velocity profile across theinterstitial cross section.

19. A burner comprising,

an inner assembly, comprising a central conduit with a downstream endand an upstream end, said upstream end being open for admitting a firstreactant stream and said downstream end being sealed around a pluralityof tubes in symmetrical spaced relationship without touching each other,said tubes being parallel to each other and to the burner axis andextending downstream from the exit end of said central conduit and incommunication therewith, and said tubes having downstream ends fordischarging said first reactant stream; first open-ended coaxialconcentric conduit disposed around the outside of said inner assemblyand in spaced relationship therewith for providing a passageway for asecond reactant stream, said cooling'means in contact with the tipsection of said second coaxial concentric conduit, said cooling meanscomprising a face-cooling plate at the discharge end of said burner andcooling coils encircling said tip section, said face-cooling plate beinghollowed out for circulating a coolant.

20. The burner as described in claim 19 wherein said temperaturemoderator is selected from the group consisting of steam, carbondioxide, atomized liquid water, cooled portion of product gas, cooledoff-gas from an ore-reduction zone, and an inert gas such as nitrogen,

and mixtures thereof.

UNHPID STATES PA'IENT OFFICE CERTZFECATE Q5? QGRRECZEQN PATENT NO.3,758,037 May 27 1975 DATED September 11, 1973 INVENTQRK'S) C P. MarionB. Reynolds l'r. 5 certified twat error appears in the above-identifiedpatent and that said Letters Patent a"? heat; cerrected as shown beiowia Col. 1, line 13 Change stream" 00 --steam-- Col. 1, lines 27 and 28Delete "This higher reacted a particulate carbon to acceptable levels."

I Col. 1, line 46 Change "teherebetween" to a --cherebetween- Cole 1,lines 51 and 52 Change "oil-stream" to --oilstee.m---

Col. 2, line 3 Change "modulator" to --moderator-- Q Col 'r, line 4Change "in" to -is-- Sugncd and Sealed this [SEAL] W- Day of August 1975I AfleSI.

RUTH-C. MANSON c. MARSHALL DANN a Anestmg OHM" ('ommissimwr ufPatenIsand Tr d k

2. The burner as described in claim 1 wherein said exit nozzleaccelerates the reactant stream flowing therein to a suitable highvelocity and provides a flat velocity profile across the interstitialcross section.
 3. The burner as described in claim 1 wherein saidconverging exit nozzle consists of a frusto-conical section whoseminimum diameter is downstream and normal to the axis of said centralconduit and whose maximum diameter is the inside diameter of thedownstream end of said concentric outer conduit.
 4. The burner asdescribEd in claim 1, wherein the tip section of said concentric outerconduit terminates in an American Society of Mechanical Engineers,standard long-radius nozzle.
 5. The burner as described in claim 1,wherein the exit ends of the plurality of tubes and the exit end of saidconcentric outer nozzle terminate in the same plane perpendicular to theburner axis at the downstream end of the burner.
 6. The burner asdescribed in claim 1, wherein the exit ends of all of said plurality oftubes terminate in a plane perpendicular to the axis of said coaxialconcentric conduit, and said plane is retracted upstream from thedownstream end of the tip section of said coaxial concentric conduit inorder to permit a limited degree of premixing but no burning, therebypreventing damage to the ends of the tubes and to the end of the tipsection.
 7. The burner as described in claim 1, wherein the exit ends ofall of said plurality of tubes terminate in a plane perpendicular to theaxis of said coaxial concentric conduit, and said plane is locateddownstream from the downstream end of the tip section of said coaxialconcentric conduit.
 8. The burner as described in claim 1, wherein theinside diameters of all of said plurality of tubes are equal, and thelengths of all of said tubes are equal.
 9. The burner as described inclaim 1, wherein the quantity of said tubes extending from said centralconduit is a number selected from the group consisting of 2 to 200 ormore.
 10. The burner as described in claim 1, wherein the number oftubes extending from said central conduit is selected so as to maintaina burner scale factor P/SL 48.2 n/D22 of at least 266 when an oilcontaining stream is flowing through said center conduit and an oxygencontaining stream is passing through said outer concentric conduit andthe Y ratio of the burner is 21.7 wherein: P sum of the perimeters forall of said extending tubes (based on inside tube diameter) S totalcross-sectional area of all of said extending tubes (based on insidetube diameter) n number of said extending tubes D2 inside diameter ofthe downstream end of the tip section of the concentric outer conduit. L1/2 (D2/ Square Root n - Do) Wherein Do inside diameter of each tube 12.And the Y ratio is the area of the downstream end of the tip section ofthe concentric outer conduit less the total cross sectional area of allof the tubes extending from the exit end of the central conduit based onthe outside diameter of said tubes divided by the total area of all ofsaid tubes based on the inside diameter of the tubes.
 11. The burner ofclaim 1 further provided with a second open-ended coaxial concentricconduit which is disposed about the first concentric conduit and inspaced relationship therewith, and a converging nozzle terminating saidsecond coaxial concentric nozzle so as to provide a passageway forintroducing a temperature moderating stream around the other twostreams.
 12. The burner as described in claim 1, wherein a stream ofoxygen-rich gas selected from the group consisting of air, oxygen-richair containing more than 21 mole percent O2, and substantially pureoxygen is passed through said inner assembly and a stream of hydrocarbonis passed through said concentric outer conduit.
 13. The burner asdescribed in claim 12, wherein a temperature moderator selected from thegroup consisting of steam, carbon dioxide, atomized liquid water, cooledportion of product gas, cooled off-gas from an ore-reduction zone, andan inert gas such as nitrogen, and mixtures thereof is admixed with theoxygen-rich gas, the hydrocarbon or both.
 14. The burner as described inclaim 1, wherein a stream of hydrocarbon is passed through said innerassembly and a stream of oxygen-rich gas selected from the groupconsisting of air, oxYgen-rich air containing more than 21 mole percentO2, and substantially pure oxygen is passed through said concentricouter conduit.
 15. The burner as described in claim 14, wherein atemperature moderator selected from the group consisting of steam,carbon dioxide, atomized liquid water, cooled portion of product gas,cooled off-gas from an ore-reduction zone, and an inert gas such asnitrogen, and mixtures thereof is admixed with the oxygen-rich gas, thehydrocarbon, or both.
 16. The burner as described in claim 1 providedwith a cooling means for cooling the tip section of said coaxialconcentric conduit by heat exchange with a cooling fluid.
 17. The burneras described in claim 1 provided with a cooling means for cooling thetip section of said coaxial concentric conduit by heat exchange with acooling fluid, wherein said cooling means comprises a hollowed outface-cooling plate at the downstream end of the burner and cooling coilsencircling said tip section through which circulating cooling water ispassed.
 18. A partial-combustion burner for use in introducing reactantsinto a gas generator, comprising a central passageway for introducing afirst reactant stream into said gas generator, said central passagewaycomprising a central conduit having a plurality of tubes extendingdownstream and in communication therewith, said tubes being parallel toeach other and to the burner axis and in symmetrically spacedrelationship without touching each other; and an open-ended coaxialconcentric outer conduit disposed about said central passageway and inspaced relationship therewith for providing a passageway for a secondreactant stream, said concentric conduit having a tip section forintroducing said second reactant stream into the interstices between theplurality of parallel tubes extending from said central conduit and fromthere into said gas generator, a converging exit nozzle terminating saidtip section so as to accelerate the second reactant stream to a suitablehigh velocity and to provide a flat velocity profile across theinterstitial cross section.
 19. A burner comprising, an inner assembly,comprising a central conduit with a downstream end and an upstream end,said upstream end being open for admitting a first reactant stream andsaid downstream end being sealed around a plurality of tubes insymmetrical spaced relationship without touching each other, said tubesbeing parallel to each other and to the burner axis and extendingdownstream from the exit end of said central conduit and incommunication therewith, and said tubes having downstream ends fordischarging said first reactant stream; a first open-ended coaxialconcentric conduit disposed around the outside of said inner assemblyand in spaced relationship therewith for providing a passageway for asecond reactant stream, said first concentric conduit having a tipsection which terminates in a converging exit nozzle for introducingsaid second reactant stream into the interstices between the pluralityof parallel tubes extending from said conduit and then to discharge; asecond open-ended coaxial concentric conduit which is disposed about thefirst concentric conduit and in spaced relationship therewith, and aconverging nozzle terminating said second coaxial concentric nozzle soas to provide a passageway for introducing a stream of temperaturemoderator around the other two streams; and cooling means in contactwith the tip section of said second coaxial concentric conduit, saidcooling means comprising a face-cooling plate at the discharge end ofsaid burner and cooling coils encircling said tip section, saidface-cooling plate being hollowed out for circulating a coolant.
 20. Theburner as described in claim 19 wherein said temperature moderator isselected from the group consisting of steam, carbon dioxide, atomizedliquid water, cooled portion of product gas, cooled off-gas from anore-reduction zone, and an inert gas such as nitrogen, and mixtuResthereof.